Weapons with infinite ammo are weaker than with regular ammo

AmethystDream

Prime example, I got the sling of seeking (+2 sling) with a written combat ability that it shoots +1 bullets that have +2 to hit and do 1d4+2 damage (same damage as an actual +1 bullet with an extra THACO) yet in the window for projected damage, it give a significantly lower number than when you use a +1 bullet, or even a regular bullet. Ex. Using base Aerie it shows 3-6 with just the sling 4-7 with a normal bullet and 5-8 with the +1 bullet. There is also a discrepancy on the THACO. Now it is possible that it is just not showing the added effect of the created ammo but applies the right damage, which is inconvenient but fine. Or that it is actually making the weapon and others like it weaker.

Hurricane

What you see is correct. As the description says, when no bullets are equipped, the sling deals a total damage of 1d4+2, which is 3-6, and that is what you see in the window for the projected damage.

When you use physical ammunition instead, the damage is determined by the bullets and the normal damage bonus of the sling. So if you use ordinary bullets, they do 1d4+1 damage and the sling bonus damage is +2, giving you 4-7 overall.

The same goes for the THAC0 bonus.

Weapons with magical ammunition are not necessarily "weaker" without ammunition, even if their magical ammunition doesn't do as much damage. They have other advantages, e.g. the magical ammunition uses the enchantment level of the launcher, which can make the magical ammunition more powerful than any enchanted physical ammunition.